chore(config): bump default amazon-bedrock model to claude-sonnet-5

DEFAULT_MODELS[amazon-bedrock] -> amazon-bedrock/global.anthropic.claude-sonnet-5
(was global.anthropic.claude-sonnet-4-5-20250929-v1:0). Verified invokable via
pi --list-models. Folded into the existing Unreleased changelog entry; openai
(gpt-5.4) default unchanged.

rootfs/usr/local/lib/opencode-devbox/generate-config.py

@@ -43,9 +43,7 @@ from pathlib import Path
 DEFAULT_MODELS: dict[str, str] = {
     "anthropic": "anthropic/claude-sonnet-5",
     "openai": "openai/gpt-5.4",
-    "amazon-bedrock": (
-        "amazon-bedrock/global.anthropic.claude-sonnet-4-5-20250929-v1:0"
-    ),
+    "amazon-bedrock": "amazon-bedrock/global.anthropic.claude-sonnet-5",
 }
 
 # Fallback when OPENCODE_PROVIDER is set but not recognized.